The present invention is directed to compositions, compounds and methods for the mineralization of various physiological tissues, primarily of bone and teeth. Mineralized connective tissue or tissues include teeth, bone, and various connective tissues such as collagen, cartilage, tendons, ligaments and other dense connective tissue and reticular fibers (that contains type III collagen) of a mammal, including a human being. For purposes of definition in this specification, “mineralized tissue” shall mean bone and teeth specifically. Each of the terms “mineralization”, “tissue mineralization”, used interchangeably herein, means a process in which crystals of calcium phosphate are produced by bone-forming cells or tooth-forming cells and laid down in precise amounts within the fibrous matrix or scaffolding of the mineralized tissue as defined hereinabove.
Calcium phosphates are a class of minerals containing, but not limited to, calcium ions together with orthophosphates, metaphosphates and/or pyrophosphates that may or may not contain hydrogen or hydroxide ions.
For purposes of definition in this specification, “remineralization” is the process of restoring minerals, in the form of mineral ions, to the hydroxyapatite latticework structure of a tooth. As used herein, the term “remineralization” includes mineralization, calcification, re-calcification and fluoridation as well as other processes by which various particular ions are mineralized to the tooth. The term “teeth” or “tooth” as used herein includes the dentin, enamel, pulp and cementum of a tooth within the oral cavity of an animal, including a human being.
In certain embodiments, the present invention provides methods for whitening the surface of a tooth material by using the compositions of the invention. For purposes of definition in this specification, as referred to herein, a “tooth material” refers to natural teeth, dentures, dental plates, fillings, caps, crowns, bridges, dental implants, and the like, and any other hard surfaced dental prosthesis either permanently or temporarily fixed to a tooth within the oral cavity of an animal, including a human being. As used herein, the terms “whitening” and “tooth whitening” used interchangeably, refer to a change in the visual appearance of a tooth as defined herein, preferably such that the tooth has a brighter shade or luster.
Conditions of the Bone
No currently practiced therapeutic strategy involves methods or compositions that sufficiently stimulate or enhance the growth of new bone mass. The present invention provides compositions, products and methods which serve to increase bone mineralization at localized sites or remineralization of teeth directly in the oral cavity, and thus may be utilized in conjunction with treatments of a wide variety of conditions where it is desired to increase bone or tissue mass as a result of any condition which can be improved by bioavailability of physiological salts, particularly of calcium and phosphate.
Certain changes in bone mass occur over the life span of an individual. After about the age of 40 and continuing to the last stages of life, slow bone loss occurs in both men and women. Loss of bone mineral content can be caused by a variety of conditions, and may result in significant medical problems. If the process of tissue mineralization is not properly regulated, the result can be too little of the mineral or too much—either of which can compromise bone health, hardness and strength. A number of bone growth disorders are known which cause an imbalance in the bone remodeling cycle. Chief among these are metabolic bone diseases such as osteoporosis, osteoplasia (osteomalacia), chronic renal failure and hyperparathyroidism, which result in abnormal or excessive loss of bone mass known as osteopenia. Other bone diseases, such as Paget's disease, also cause excessive loss of bone mass at localized sites.
Osteoporosis is a structural deterioration of the skeleton caused by loss of bone mass resulting from an imbalance in bone formation, bone resorption, or both. Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood. Bone resorption dominates the bone formation phase, thereby reducing the weight-bearing capacity of the affected bone. In a healthy adult, the rate at which bone is formed and resorbed is tightly coordinated so as to maintain the renewal of skeletal bone. However, in osteoporotic individuals, an imbalance in these bone remodeling cycles develops which results in both loss of bone mass and in formation of micro-architectural defects in the continuity of the skeleton. These skeletal defects, created by perturbation in the remodeling sequence, accumulate and finally reach a point at which the structural integrity of the skeleton is severely compromised and bone fracture is likely. Although this imbalance occurs gradually in most individuals as they age, it is much more severe and occurs at a rapid rate in postmenopausal women. In addition, osteoporosis also may result from nutritional and endocrine imbalances, hereditary disorders and a number of malignant transformations.
Osteoporosis in humans is preceded by clinical osteopenia (bone mineral density that is greater than one standard deviation but less than 2.5 standard deviations below the mean value for young adult bone), a condition found in approximately 25 million people in the United States. Another 7-8 million patients in the United States have been diagnosed with clinical osteoporosis (defined as bone mineral content greater than 2.5 standard deviations below that of mature young adult bone). Osteoporosis is one of the most expensive diseases for the health care system, costing billions of dollars annually in the United States. In addition to health care related costs, long-term residential care and lost working days add to the financial and social costs of this disease. Worldwide, approximately 75 million people are at risk for osteoporosis.
The frequency of osteoporosis in the human population increases with age, and among Caucasians is predominant in women, who comprise approximately 80% of the osteoporosis patient pool in the United States. In addition in women, another phase of bone loss occurs possibly due to postmenopausal estrogen deficiencies. During this phase of bone loss, women can lose an additional 10% in the cortical bone and 25% from the trabecular compartment. The increased fragility and susceptibility to fracture of skeletal bone in the aged is aggravated by the greater risk of accidental falls in this population. More than 1.5 million osteoporosis-related bone fractures are reported in the United States each year. Fractured hips, wrists, and vertebrae are among the most common injuries associated with osteoporosis. Hip fractures in particular are extremely uncomfortable and expensive for the patient, and for women correlate with high rates of mortality and morbidity.
Patients suffering from chronic renal (kidney) failure almost universally suffer loss of skeletal bone mass, termed renal osteodystrophy. While it is known that kidney malfunction causes a calcium and phosphate imbalance in the blood, to date replenishment of calcium and phosphate by dialysis does not significantly inhibit osteodystrophy in patients suffering from chronic renal failure. In adults, osteodystrophic symptoms often are a significant cause of morbidity. In children, renal failure often results in a failure to grow, due to the failure to maintain and/or to increase bone mass.
Osteoplasia, also known as osteomalacia (“soft bones”), is a defect in bone mineralization (e.g., incomplete mineralization), and classically is related to vitamin D deficiency (1,25-dihydroxy vitamin D3). The defect can cause compression fractures in bone, and a decrease in bone mass, as well as extended zones of hypertrophy and proliferative cartilage in place of bone tissue. The deficiency may result from a nutritional deficiency (e.g., rickets in children), malabsorption of vitamin D or calcium, and/or impaired metabolism of the vitamin.
Hyperparathyroidism (overproduction of the parathyroid hormone) is known to cause malabsorption of calcium, leading to abnormal bone loss. In children, hyperparathyroidism can inhibit growth, in adults the skeleton integrity is compromised and fracture of the ribs and vertebrae are characteristic. The parathyroid hormone imbalance typically may result from thyroid adenomas or gland hyperplasia, or may result from prolonged pharmacological use of a steroid. Secondary hyperparathyroidism also may result from renal osteodystrophy. In the early stages of the disease, osteoclasts are stimulated to resorb bone in response to the excess hormone present. As the disease progresses, the trabecular bone ultimately is resorbed and marrow is replaced with fibrosis, macrophages and areas of hemorrhage as a consequence of microfractures, a condition is referred to clinically as osteitis fibrosa.
Paget's disease (osteitis deformans) is a disorder currently thought to have a viral etiology and is characterized by excessive bone resorption at localized sites which flare and heal but which ultimately are chronic and progressive, and may lead to malignant transformation. The disease typically affects adults over the age of 25.
Although osteoporosis has been defined as an increase in the risk of fracture due to decreased bone mass, none of the presently available treatments for skeletal disorders can substantially increase the bone density of adults. A strong perception exists among physicians that drugs are needed which could increase bone density in adults, particularly in the bones of the wrist, spinal column and hip that are at risk in osteopenia and osteoporosis.
Current strategies for the prevention of osteoporosis may offer some benefit to individuals but cannot ensure resolution of the disease. These strategies include moderating physical activity, particularly in weight-bearing activities, with the onset of advanced age, including adequate calcium in the diet, and avoiding consumption of products containing alcohol or tobacco. For patients presenting with clinical osteopenia or osteoporosis, all current therapeutic drugs and strategies are directed to reducing further loss of bone mass by inhibiting the process of bone absorption, a natural component of the bone remodeling process that occurs constitutively.
For example, estrogen is now being prescribed to retard bone loss. There is, however, some controversy over whether there is any long term benefit to patients and whether there is any effect at all on patients over 75 years old. Moreover, use of estrogen is believed to increase the risk of breast and endometrial cancer. High doses of dietary calcium with or without vitamin D have also been suggested for postmenopausal women. However, ingestion of high doses of calcium can often have unpleasant gastrointestinal side effects, and serum and urinary calcium levels must be continuously monitored.
Other therapeutics which have been suggested include calcitonin, bisphosphonates, anabolic steroids and sodium fluoride. Such therapeutics however, have undesirable side effects, for example, calcitonin and steroids may cause nausea and provoke an immune reaction, bisphosphonates and sodium fluoride may inhibit repair of fractures, even though bone density increases modestly, which that may prevent their usage.
The above disorders are examples of conditions that may lead to bone fractures, fissures or splintering of the bones in the individuals who suffer from a given disorder. Current therapeutic methods are insufficient to treat the disorders leaving a need for improved treatments of bone fractures when they occur in the individual. The present invention provides improved compositions, products and methods for locally treating bone fractures, fissures, splintering and similar breakages of the bone, or by strengthening decomposed bone tissue by increasing the mechanism of mineralization of the bone. It is conceivable that the current invention also causes mineralization of the surrounding connective tissue, such as collagen, cartilage, tendons, ligaments and other dense connective tissue and reticular fibers.
The Oral Cavity
With respect to tissue decomposition in the oral cavity, it is commonly known in the dental art that certain kinds of tooth decomposition and decay that occurs over time in the mouth is initiated by acid etching of the tooth enamel with the source of the acid being a metabolite resulting from bacterial and enzymatic action on food particles in the oral cavity. It is generally understood that plaque, a soft accumulation on the tooth surface consisting of an organized structure of microorganisms, proteinaceous and carbohydrate substances, epithelial cells, and food debris, is a contributory factor in the development of various pathological conditions of the teeth and soft tissue of the oral cavity. The saccharolytic organisms of the oral cavity which are associated with the plaque, cause a demineralization or decalcification of the tooth beneath the plaque matrix through metabolic activity which results in the accumulation and localized concentration of organic acids. The etching and demineralization of the enamel may continue until they cause the formation of dental caries and periodontal disease within the oral cavity.
Teeth are cycled through periods of mineral loss and repair also as a result of pH fluctuations in the oral cavity. The overall loss or gain of mineral at a given tooth location determine whether the carious process will regress, stabilize or advance to an irreversible state. Numerous interrelated patient factors affect the balance between the remineralization and demineralization portions of this cycle and include oral hygiene, diet, and the quantity and quality of saliva. At the most extreme point in this process, a restoration will be required to repair the tooth.
Methods for the prevention and reduction of plaque and tooth decay within the oral cavity commonly involve the brushing of the teeth using toothpastes; mechanical removal of the plaque with dental floss; administration and rinsing of the oral cavity with mouthwashes, dentifrices, and antiseptics; remineralization and whitening of the teeth with fluoride agents, calcium agents and whitening agents, and various other applications to the oral cavity. Still missing in the field is a delivery system for the remineralization of teeth that would address the challenges of demineralization facing the teeth continually in the oral cavity.
A tooth that has reached an advanced stage of decay often requires installation of a dental restoration within the mouth. Half of all dental restorations fail within 10 years, and replacing them consumes 60% of the average dentist's practice time. Current dental materials are challenged by the harsh mechanical and chemical environment of the oral cavity with secondary decay being the major cause of failure. Development of stronger and longer-lasting biocompatible dental restorations by engineering novel dental materials or new resin systems, enhancing existing materials, and incorporating bioactive agents in materials to combat microbial destruction and to sustain the harsh mechanical and chemical environment of the oral cavity continues to be desired.
Despite numerous preventive oral health strategies, dental caries remains a significant oral health problem. More than 50% of children aged 6-8 will have dental caries and over 80% of adolescents over age 17 will have experienced the disease. Caries is also seen in adults both as a primary disease and as recurrent disease in already treated teeth. Advances in diagnosis and treatment have led to non-invasive remineralizing techniques to treat caries. However mechanical removal of diseased hard tissue and restoration and replacement of enamel and dentin is still the most widely employed clinical strategy for treating primary caries, restoring function to the tooth and also blocking further decay. In addition, nearly 50% of newly placed restorations are replacement of failed restorations. Clearly, restorative materials are a key component of treating this widespread disease.
The selection of a restorative material has significantly changed in recent years. While dental amalgam is still considered a cost effective material, there is a growing demand for tooth colored alternatives that will provide the same clinical longevity that is enjoyed by dental amalgam. The use of composite resins has grown significantly internationally as a material of choice for replacing amalgam as a restorative material for posterior restorations. This demand is partially consumer driven by preference for esthetic materials and the concerns regarding the mercury content of amalgam. It is also driven by dentists recognizing the promise of resin-based bonded materials in preserving and even supporting tooth structure. Numerous studies have suggested that bonding the restoration to the remaining tooth structure decreases fracture of multi-surface permanent molar preparations. Unfortunately, posterior teeth restored with direct resin restorative materials have a higher incidence of secondary caries. This has led to shorter clinical service and narrower clinical indications for composite resin materials compared to amalgam.
The most frequently cited reason for restoration replacement is recurrent decay around or adjacent to an existing restoration. It is likely that fracture at the margin due to polymerization shrinkage can lead to a clinical environment at the interface between a restoration and the tooth that collects dental plaque and thus promotes decay. Therefore, developing dental materials with anti-caries capability is a very high priority for extending the longevity of restorations.
Tooth Remineralization
Although natural remineralization is always taking place in the oral cavity, the level of activity varies according to conditions in the mouth as discussed. Incorporation of fluoride during the remineralization process has been a keystone for caries prevention. The effectiveness of fluoride release from various delivery platforms, including certain dental restorative materials has been widely demonstrated. It is commonly accepted that caries prevention from fluoride is derived from its incorporation as fluorapatite or fluoride enriched hydroxyapatite in the tooth mineral thereby decreasing the solubility of tooth enamel. More recently, anti-caries activity has been demonstrated using the strategy of increasing solution calcium and phosphate concentrations to levels that exceed the ambient concentration in oral fluids. In order for fluoride to be effective at remineralizing previously demineralized enamel, a sufficient amount of calcium and phosphate ions must be available. For every two (2) fluoride ions, ten (10) calcium ions and six (6) phosphate ions are required to form a cell of fluorapatite (Ca10(PO4)6F2). Thus the limiting factor for net enamel remineralization is the availability of calcium and fluoride in saliva.
The low solubility of calcium phosphates has limited their use in clinical delivery platforms, especially when in the presence of fluoride ions. These insoluble phosphates can only produce available ions for diffusion into the enamel in an acidic environment. They do not effectively localize to the tooth surface and are difficult to apply in clinically usable forms. Because of their intrinsic solubility, soluble calcium and phosphate ions can only be used at very low concentrations. Thus they do not produce concentration gradients that drive diffusion into the subsurface enamel of the tooth. The solubility challenge is exacerbated by the even lower solubility of calcium fluoride phosphates.
Several commercially available approaches exist using calcium and phosphate preparations that have been commercialized into various dental delivery models. These have been reportedly compounded to overcome the limited bioavailability of calcium and phosphate ions for the remineralization process. The first technology uses casein phosphopeptide (CCP) stabilized with amorphous calcium phosphate (ACP) (RECALDENT® CCP-ACP of Cadbury Enterprises Pte. Ltd.). It is hypothesized that the casein phosphopeptide can facilitate the stabilization of high concentrations of ionically available calcium and phosphate even in the presence of fluoride. This formulation binds to pellicle and plaque and while the casein phosphopeptide prevents the formation of dental calculus, the ions are available to diffuse down the concentration gradient to subsurface enamel lesions facilitating remineralization. As compared to the CCP-ACP, in the composition of the invention, biologically available ions are available due to the fact that the salts are already solvated in the microcapsule of the invention. Amorphous calcium phosphate is not soluble in water or saliva. Although the manufacturer claims release of bioavailable ions from amorphous calcium phosphate, it is not as a result of the dissolution of the complex. A second technology (ENAMELON®) uses unstabilized amorphous calcium phosphate. Calcium ions and phosphate ions are introduced as a dentifrice separately in a dual chamber device forming amorphous calcium phosphate in-situ. It is proposed that formation of the amorphous complex promotes remineralization. A third approach uses a so-called bioactive glass (NOVAMIN® of NovaMin Technology Inc.) containing calcium sodium phosphosilicate. It is proposed that the glass releases calcium and phosphate ions that are available to promote remineralization. More recently dental composite formulations have been compounded using zirconia-hybridized ACP that may have the potential for facilitating clinical remineralization.
While the Recaldent® and Enamelon® preparations have both in-situ and in-vivo evidence suggesting enhanced remineralization, these are topically applied and do not specifically target the most at risk location for recurrent caries at the tooth restoration interface. While the bioactive glass and the zirconia-hybridized-ACP filler technologies have potential, they are relatively inflexible in terms of the range of formulations in which they might be used due to the challenges of dealing with brittle fillers and some of the limitations on controlling filler particle size.
Another approach taken to decrease caries in the oral cavity is the limiting of demineralization of enamel and bone by drinking water fluoridation. It has been shown that the fluoride contained in drinking water incorporates to some extent into hydroxyapatite, the major inorganic component of enamel and bone. Fluoridated hydroxyapatite is less susceptible to demineralization by acids and is thus seen to resist the degradation forces of acidic plaque and pocket metabolites. In addition, fluoride ion concentration in saliva is increased through consumption of fluoridated drinking water. Saliva thus serves as an additional fluoride ion reservoir and in combination with buffering salts naturally found in salivary fluid, fluoride ions are actively exchanged on the enamel surface, further offsetting the effects of demineralizing acid metabolites.
Notwithstanding the established benefits of fluoride treatment of teeth, fluoride ion treatment can result in irregular spotting or blotching of the teeth depending on the individual, whether administered through drinking water or by topically applied fluoride treatment. This effect is known to be both concentration related and patient specific. In addition, the toxicology of fluoride is being studied as to its long term effect on human health. Desired is a targeted approach of fluoridation in the oral cavity.
Another approach to limiting the proliferation of microflora in the oral environment is through topical or systematic application of broad-spectrum antibacterial compounds. Reducing the number of oral microflora in the mouth results in a direct reduction or elimination of plaque and pocket accumulation together with their damaging acidic metabolite production. The major drawback to this particular approach is that a wide variety of benign or beneficial strains of bacteria are found in the oral environment which may be killed by the same antibacterial compounds in the same manner as the harmful strains. In addition, treatment with antibacterial compounds may select for certain bacterial and fungi, which may then become resistant to the antibacterial compound administered and thus proliferate, unrestrained by the symbiotic forces of a properly balanced microflora population. Thus the application or administration of broad-spectrum antibiotics alone is ill-advised for the treatment of caries and a more specific, targeted approach is desired.
Tooth Whitening
Cosmetic dental whitening or bleaching has become extremely desirable to the general public. Many individuals desire a “bright” smile and white teeth, and consider dull and stained teeth cosmetically unattractive. Unfortunately, without preventive or remedial measures, stained teeth are almost inevitable due to the absorbent nature of dental material. Everyday activities such as eating, chewing, or drinking certain foods and beverages (in particular coffee, tea, and red wine) and smoking or other oral use of tobacco products cause undesirable staining of surfaces of teeth. Extrinsic staining of the acquired pellicle arises as a result of compounds such as tannins and polyphenolic compounds which become trapped in and tightly bound to the proteinaceous layer on the surfaces of teeth. This type of staining can usually be removed by mechanical methods of tooth cleaning. In contrast, intrinsic staining occurs when staining compounds penetrate the enamel and even the dentin or arise from sources within the tooth. The chromogens or color causing substances in these materials become part of the pellicle layer and can permeate the enamel layer. Even with regular brushing and flossing, years of chromogen accumulation can impart noticeable tooth discoloration. Intrinsic staining can also result from microbial activity, including that associated with dental plaque. This type of staining is not amenable to mechanical methods of tooth cleaning and chemical methods are required.
Without specifically defining the mechanism of action of the present invention, the compositions, products and methods of the present invention enable the precipitation of salts onto the surfaces of the teeth in the oral cavity and make the salts available for adherence to the tooth surface and remineralization of the teeth. The mineralizing salts are deposited in the interstitial spaces of the teeth, making the teeth smoother, increasing the reflection of light from the surface of the teeth and thereby giving the teeth a brighter, more lustrous appearance and whiter visual effect.
Tooth whitening compositions generally fall into two categories: (1) gels, pastes, varnishes or liquids, including toothpastes that are mechanically agitated at the stained tooth surface in order to affect tooth stain removal through abrasive erosion of stained acquired pellicle; and (2) gels, pastes, varnishes or liquids that accomplish the tooth whitening effect by a chemical process while in contact with the stained tooth surface for a specified period, after which the formulation is removed. In some cases, the mechanical process is supplemented by an auxiliary chemical process which may be oxidative or enzymatic. Initially, tooth whitening had been performed at the dentist's office. Less expensive at-home dental whitening kits have become available, such as whitening strips and whitening trays that come in either single compartment or dual compartment systems.
Both in-office and at-home tooth whitening typically involves the application of a peroxide containing composition to the surface of the tooth to achieve the desired whitening effect. The majority of most in-office and at-home tooth whitening compositions act by oxidation. These compositions are applied directly by a patient in a tooth-bleaching tray, held in place in the mouth for contact times, sometimes for periods of half an hour several times per day; or of greater than 60 minutes per day, and sometimes as long as 8 to 12 hours. The slow rate of bleaching is, in large part, the consequence of formulations that are developed to maintain stability of the oxidizing composition. Aqueous tooth whitening gels have proven desirable due to the hydrating effects on the structure of the tooth, reducing the likelihood of tooth sensitivity.
The most commonly used oxidative compositions contain the hydrogen peroxide precursor carbamide peroxide which is mixed with an anhydrous or low-water content, hygroscopic viscous carrier containing glycerine and/or propylene glycol and/or polyethylene glycol. When contacted by water, carbamide peroxide dissociates into urea and hydrogen peroxide. The latter has become the tooth bleaching material of choice due to its ability to whiten teeth faster than higher concentrations of carbamide peroxide.
An alternative source of hydrogen peroxide is sodium percarbonate and this has been used in a silicone polymer product that is painted onto the teeth forming a durable film for overnight bleaching procedures. The peroxide is slowly released for up to 4 hours.
Associated with the slow rate of bleaching-in the hygroscopic carrier, the currently available tooth-bleaching compositions cause tooth sensitization in over 50% of patients. Tooth sensitivity is believed to result from the movement of fluid through the dentinal tubes toward nerve endings in the tooth. This movement is enhanced by the carriers for the carbamide peroxide. It has been determined that glycerine, propylene glycol and polyethylene glycol can each give rise to varying amounts of tooth sensitivity following exposure of the teeth to heat, cold, overly sweet substances, and other causative agents.
Hydrogen peroxide tooth bleaching formulations have limitations in addition to tooth sensitivity. Until recent years, stable aqueous hydrogen peroxide tooth bleaching gels have been virtually non-existent. Hydrogen peroxide is a powerful oxidizing agent and an unstable compound that decomposes readily over time into water and oxygen. Certain chemical and physical influences in the oral cavity can accelerate the rate of decomposition and need to be controlled for a stable tooth whitening gel to exist. Temperature, pH and errant metal ions all have a profound effect on the decomposition of hydrogen peroxide, particularly in an aqueous formula.
One advantage of the compositions of the invention is the decrease or elimination of tooth sensitivity of the patient. When used in conjunction with current tooth bleaching products, the microcapsules of the invention release salt ions that precipitate as salts in the oral cavity and mineralize the open dentin tubules of the teeth thereby decreasing tooth sensitivity to the oxidative tooth bleaching product.
Whitening systems on the market include two-part systems that require mixing of the components upon administration and single part compositions that are faster and easier to administer and generally preferred for in-office bleaching by dentists. Two-part systems include products such as dual barrel syringes, liquid hydrogen peroxide/powder systems and whitening strips. Single component tooth bleaching compositions prefer room temperature storage conditions in order to eliminate costly and inconvenient storage problems. The pH of an aqueous hydrogen peroxide tooth whitening composition also has great bearing on the stability of the formulation. The two-part systems demonstrate superior shelf life stability. Formulations that contain hydrogen peroxide solutions are strongly acidic and maintain their stability in acidic pH formulas. Stable aqueous hydrogen peroxide tooth whitening gels can be formulated in the acid pH range. However, bleaching compositions in the acidic pH range (pH 2.0-5.5) are prone to the demineralization of dental enamel by the solubilizing of calcium ions from the tooth surface. This reduction in surface enamel leads to tooth sensitivity and discomfort for the patient. By incorporating the compositions of the invention into tooth bleaching products or utilizing them in conjunction with tooth bleaching products, the microcapsules of the invention can modify the pH level in the oral cavity to cause acceleration of the bleaching process.
Many of the available products are time-consuming and limited in their effectiveness and subject the user to various physical discomforts. More importantly, it has been shown that prolonged exposure of teeth to whitening compositions, as practiced at present, has a number of adverse effects in addition to that of tooth sensitivity. Over time, any of the peroxides known in the art to achieve a desired tooth bleaching effect will function as calcium chelating agents. Other examples of chelation agents often found in tooth whitening products include EDTA and its salts, citric acid and its salts, gluconic acid and its salts, alkali metal pyrophosphates and alkali metal polyphosphates. Solubilization of calcium from the enamel layer can occur at a pH less than 5.5 with associated demineralization. The chelating agents will penetrate the intact enamel and dentin so as to reach the pulp chamber of a vital tooth thereby risking damage to pulpal tissue. Other adverse effects include dilution of the bleaching compositions with saliva in the oral cavity with resulting leaching from the dental tray and subsequent digestion by the user.
It has been shown that the rate of whitening can be increased by increasing the temperature of the hydrogen peroxide system, where increase of 10.degree. C. can double the rate of reaction. Consequently, there exist a number of procedures that utilize high-intensity light to raise the temperature of the hydrogen peroxide to accelerate the rate of bleaching of the teeth. Other approaches to heating the hydrogen peroxide have been described such as the heating of dental instruments. Contemporary approaches and literature have focused on accelerating peroxide bleaching with simultaneous illumination of the anterior teeth with various sources having a range of wavelengths and spectral power, for example, halogen curing lights, plasma arc lamps, lasers and light-emitting diodes. Some products that are used in light activated whitening procedures contain ingredients that serve as photosensitizers that claim to aid the energy transfer from the light to the peroxide gel and are often colored materials, for example carotene and manganese sulfate. However, excessive heating can cause irreversible damage to the dental pulp. In addition, the literature for in vitro and clinical studies and actual results demonstrate that the actual effect of light on tooth whitening is limited, conflicting and controversial.
There is thus a need for improved compositions, methods and products that overcome the limitations of the prior art. The challenge remains to create a tooth whitening and remineralization technology platform for incorporating stable and effective tissue remineralization ions that can be incorporated into a myriad of dental materials and variety of products. Such a delivery platform would facilitate the formulation of dental products capable of remineralization of the teeth. The compositions, products and methods of the current inventions as described herein satisfy these and other needs. The ultimate impact is a reduction in recurrent caries, the most prevalent reason for restoration replacement; whitening of the teeth; and resulting improvement in overall strength and health of the teeth in the oral cavity.
There exists a broad need for improved compositions and methods useful for therapeutic agent delivery. In particular, there is a need for an improved microcapsule-based technology for delivering therapeutic agents to diverse tissue types in a stable and time-controlled manner.